The present invention related to 6 KHz and above gas discharge laser systems, such as ArF, KrF, F.sub.2, XeCl and the like gas discharge lasers.
Gas discharge lasers, e.g., in a MOPA configuration, e.g., applicants' assignee's XLA-100 series laser systems, employing a master oscillator and power amplifier based ArF excimer gas discharge laser, e.g., for use in various applications, e.g., as a microlithography DUV light source have demonstrated performance and stability that were unattainable by the traditional single oscillator line-narrowed laser design. The MOPA design uses two discharge chambers. The master oscillator (MO) generates an extremely line-narrowed laser beam, e.g., at around 193 nm for an ArF laser, with a relatively small energy content, typically around 1 mJ. The power amplifier (PA) amplifies the laser pulse from the MO. The beam from the MO can, e.g., traverse the power amplifier's gain region, e.g., making one round trip, e.g., timed to amplify some portion of the output pulse of the MO by initiating and sustaining a discharge while that portion of the MO output pulse is traversing the PA within the lasing medium between the electrodes of the PA with lasing occurring almost exclusively at the line narrowed center wavelength of the MO output.
A summary of the XLA-100 key performance and expected lifetimes is presented in Table 1 below. TABLE-US-00001 TABLE 1 Parameter Value Average Output Power 40 W Maximum repetition rate 4 kHz Energy Dose stability (20 ms window) <0.3% Operational Pulse Energy 8.5-11.5 mJ Peak energy density <30 mJ/cm.sup.2 Temporal pulse width >44 ns (Integral Square definition) Wavelength Tuning Range 193.200 nm-193.500 nm Spectral Bandwidth, FWHM <0.25 pm Spectral Bandwidth, E95%<0.65 pm Short term Wavelength stability <.+−.20 fm (20 ms window) Gas life 100M shots, 72 hours Chambers PA 16 B pulses, MO 12 B pulses LNM 12 B pulses LAM and SAM 20 B pulses.
The extremely narrow output spectrum of the XLA-100 enables scanners with an NA greater than 0.9. Higher average output power improves the wafer throughput of the scanner. In addition, extended lifetimes of discharge chambers help to control the operating cost. Variable energy and repetition rate capabilities provide scanners with a freedom to use the optimum laser operating modes for any processes, thus always ensuring the best results.
The MOPA system for certain applications, e.g., as a drive laser for a laser produced plasma (“LPP”) extreme ultraviolet (“EUV”), sometimes called soft x-ray or a low temperature polycrystalline silicon laser annealing apparatus, e.g., for the manufacture of thin film transistors, e.g., for flat panel display uses, demand, among other things, higher pulse repetition rates. In the former case, this may be, e.g., to produce plasma formations, e.g., from liquid droplet targets, at a sufficiently high rate to extract enough wattage from relatively low energy plasmas for, e.g., microlithography use, and in the latter to deliver high enough laser power to a relatively large workpiece (hundreds of cm on a side) for effective throughput of a laser annealing apparatus.
Cooling electrical components, e.g., in a solid state pulse power system, e.g., magnetic switch components is discussed in U.S. patent application Ser. No. 10/607,407, filed Jun. 25, 2003, entitled “Method and Apparatus for Cooling Magnetic Circuit Elements,”, U.S. Pat. No. 5,448,580, entitled AIR AND WATER COOLED MODULATOR, issued to Birx, et. al. on Sep. 5, 1995, and U.S. Pat. No. 6,240,112, entitled HIGH PULSE RATE PULSE POWER SYSTEM WITH LIQUID COOLING, issued to Partlo, et al. on May 29, 2001 and U.S. Pat. No. 4,983,859, MAGNETIC DEVICE FOR HIGH VOLTAGE-PULSE GENERATING APPARATUSES, issued to Nakajima, et al. on Jan. 8, 1991, the disclosures of each of which is hereby incorporated by reference.